1. Field of the Invention
The present invention generally relates to a control technology for bi-stable displaying, in particular, to a control method for bi-stable displaying which adopts a queue architecture and is capable of improving display speed and quality, and a timing controller (TCON) and a display control device applying the method.
2. Description of Related Art
As far as current display technologies are concerned, besides large-scale display technologies generally applied to household or end consumers, such as liquid crystal displays, plasma displays, or conventional cathode-ray tube televisions, flexible display technologies adopting new generation materials tend to be gradually attracting attention. In current various display technologies, a bi-stable display technology attracts the most attention next to an organic light emitting diode (OLED) display technology. The bi-stable display technology has been universally applied to electronic book technologies up to the present. Through persistent development, it tends to become a new generation flexible display to replace paper in future. Currently, several different bi-stable display technologies, i.e., cholesteric liquid crystal and electronic ink (e-ink) technologies, have been developed, both being current mainstream technologies.
As the name implies, bi-stable means that a display cell is capable of persistently maintaining either of two different states, namely, a bright state and a dark state, without any voltage applied. In other words, the bi-stable technology enables picture memorization with no voltage applied, thereby having an advantage of low power consumption. In an ideal state, a display of the bi-stable technology may save up to hundreds of times of electric quantity as compared with the conventional liquid crystal display technology, and thus is quite suitable to be applied in occasions without the need of frequently updating a picture, such as mobile phones, electronic books, and even large-scale electronic display boards.
Referring to FIG. 1, it is a schematic block diagram of a basic architecture of a conventional bi-stable display device. A timing controller (TCON) 130 mainly used for controlling all input and output timings is disposed in the conventional bi-stable display device 100. The TCON 130 receives image data sent by a central processing unit (CPU) 110 through a host interface 120.
Moreover, the TCON 130 is coupled to a memory 150. The memory 150 is divided into a current frame buffer 152 and a previous frame buffer 154. The current frame buffer 152 is used for temporarily storing display data (such as including color data of a pixel) of an image to be displayed currently, while the previous frame buffer 154 is used for temporarily storing display data (such as including color data of a pixel) of an image that has been completely displayed on a panel 170.
Moreover, the conventional bi-stable display device 100 further includes a look up table (LUT) 140, which is used for recording all possible driving voltage waveforms. The content of the LUT 140 usually includes all possible combinations of previous display data and current display data, and driving voltage data corresponding to all the possible combinations respectively. In this way, the TCON 130 may obtain driving voltage data of each pixel in an image by referring to the LUT 140 according to previous and current display data of each pixel stored in the memory 150.
Moreover, the TCON 130 is also connected to a driving circuit 172 through a display interface 160 and a transmission line 162. After obtaining the driving voltage data, the TCON 130 may provide the driving voltage data to the driving circuit 172 through the display interface 160 and the transmission line 162. Accordingly, the driving circuit 172 is capable of generating a corresponding driving voltage to drive the panel 170 to display an image. For example, the driving voltage data of “00b” or “11b” represents that the driving voltage is 0 V; the driving voltage data of “01b” represents that the driving voltage is +15 V; and the driving voltage data of “10b” represents that the driving voltage is −15 V.
Referring to FIGS. 2A and 2B, they are respectively waveform diagrams of driving voltages generated by the driving circuit 172 respectively when a black picture and a white picture are displayed. As shown in FIGS. 2A and 2B, the driving voltages generated by the black picture and the white picture respectively are maintained at +15 V and −15 V during a complete update time T0. The complete update time T0 represents a time for replacing an entire picture, while a time T1 represents a frame execution time. The complete update time T0 is integer times of the frame execution time T1. For example, T0 is about 260 milliseconds (ms), while T1 is about 20 ms.
Operating principles of elements in the conventional bi-stable display device 100 are illustrated in detail hereinafter by taking display of a black image as an example first. First, referring to FIG. 3A, it illustrates an image format of a black image received by the TCON 130. As shown in FIG. 3A, this black image is presented as a rectangular area, and format data of the image includes data such as starting point coordinates (X1, Y1) of this rectangular area R, image pixels, an image width (W), and an image length (L).
Then, referring to FIG. 3B, it includes FIGS. 3B-1 to 3B-3 for illustrating the content stored in the current frame buffer 152 and the previous frame buffer 154 and the content displayed on the panel 170 of the black image in FIG. 3A in different stages of processing and display processes. It is assumed that both the current frame buffer 152 and the previous frame buffer 154 are blank at the beginning, as shown in FIG. 3B-1.
Next, after receiving the display data of the rectangular area R from the host interface 120, the ICON 130 firstly stores the display data (including a data amount of W×L pixels) of this rectangular area R into the current frame buffer 152, as shown in FIG. 3B-2.
Next, the TCON 130 obtains driving data required for displaying each pixel of the rectangular area R by referring to the LUT 140 according to pixel data of all corresponding addresses in the current frame buffer 152 and the previous frame buffer 154, and transfers the driving data to the display interface 160 to drive the panel 170. Therefore, after one frame execution time T1 elapses, the panel 170 initially displays a black image (in a light color) of the rectangular area R. Next, the step from referring to the LUT 140 to driving the panel 170 is repeated with one frame execution time T1 spent every time, so as to gradually enhance the color of the displayed image. Until one complete update time T0 elapses, the panel 170 completely displays a black image (in a dark color) of the rectangular area R, as shown in FIG. 3B-3.
Finally, the TCON 130 replicates the display data stored in the current frame buffer 152 to a relative position of the previous frame buffer 154, so as to update the previous frame buffer 154, as shown in FIG. 3B-3 likewise.
Operating principles of the elements are further illustrated hereinafter when the conventional bi-stable display device 100 realizes such functions as pen drawing or handwriting. First, referring to FIG. 4A, it shows an example of a pen drawn image received by the TCON 130. As shown in FIG. 4A, it is assumed that a user draws three consecutive line segments in sequence with a pen: a line segment 1, a line segment 2, and a line segment 3.
Referring to FIGS. 4B-1 and 4B-2, they include FIGS. (a) to (e) for illustrating the content stored in the current frame buffer 152 and the previous frame buffer 154 and the content displayed on the panel 170 of the pen drawn image in FIG. 4A in different stages of processing and display processes. Firstly, it is assumed that both the current frame buffer 152 and the previous frame buffer 154 are blank at the beginning, as shown in FIG. (a). The CPU 110 transfers the line segment 1 as an area image to the TCON 130, so a data amount of all pixels (W1×L1) in a rectangular area R1 must be transferred.
After receiving the display data of the rectangular area R1 including the line segment 1, the TCON 130 firstly stores the display data into the current frame buffer 152, as shown in FIG. (b).
Next, the TCON 130 obtains driving data for displaying each pixel in the rectangular area R1 by referring to the LUT 140 according to display data of corresponding addresses in the current frame buffer 152 and the previous frame buffer 154, and transfers the driving data to the display interface 160 to drive the panel 170. After the step from referring to the LUT 140 to driving the panel 170 is repeated for a complete update time T0, the panel 170 completely displays the line segment 1, as shown in FIG. (c). Afterwards, the TCON 130 replicates the display data of the rectangular area R1 of the current frame buffer 152 to corresponding addresses of the previous frame buffer 154, as shown in FIG. (c) likewise.
Afterwards, the TCON 130 also receives the line segment 2. Similar to the processing and display processes of the line segment 1, the TCON 130 sequentially performs the following steps likewise. Firstly, the received display data (including a data amount of W2×L2 pixels) of a rectangular area R2 is stored into the current frame buffer 152, as shown in FIG. (c) likewise. Subsequently, driving data of each pixel of the rectangular area R2 is obtained by referring to the LUT 140, and the step is repeated for a complete update time T0 until the line segment 2 is completely displayed on the panel 170, a result of which is as shown in FIG. (d). Finally, after the line segment 2 is completely displayed, the display data of the rectangular area R2 is replicated from the current frame buffer 152 to the previous frame buffer 154, as shown in FIG. (d) likewise.
Afterwards, the TCON 130 also receives the line segment 3. Similar to the processing and display processes of the line segment 1 and the line segment 2, the TCON 130 sequentially performs the following procedures likewise. The display data (including a data amount of W3×L3 pixels) of a rectangular area R3 is stored into the current frame buffer 152, as shown in FIG. (d) likewise; the step of obtaining the driving data by referring to the LUT to drive the panel 170 is repeated for a complete update time T0, and then the line segment 3 is completely displayed, as shown in FIG. (e); and the display data is replicated to the previous frame buffer 154, as shown in FIG. (e) likewise.
However, when the pen drawing or handwriting function is executed by using the above procedures, each line segment is regarded as an area image to be processed in each processing step, so a large amount of display data is generated in each step. Moreover, only after the updating of the current frame buffer 152, comparison, and display are performed for the each line segment, the updating, comparison, and display can be continued for a next line segment. In other words, only after each line segment is processed for one complete update time T0, the processing procedure can be proceeded to process a next line segment. As a result, the driving data at any time can only include relevant driving data of a single line segment. When pen drawing or handwriting is rapidly performed, a picture is displayed too slowly, and a smooth line segment cannot be presented.